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Proceedings Paper

Alignment of master and sample in comparative digital holography
Author(s): Xavier Schwab; Eugen Meister; Giancarlo Pedrini; Wolfgang Osten
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Paper Abstract

A comparative digital holography system suitable for shape and deformation comparisons between master and sample objects with rough surfaces is described. The innovative aspect of comparative digital holography is the illumination of the sample by the conjugated wavefront of the master, as a type of coherent mask, using a liquid crystal display (LCD). The resulting interferogram indicates directly the shape or the deformation differences between the master and sample. As it is not necessary that both objects to be compared are located at the same place for this technique, remote shape or deformation comparison between a master and a sample is possible. A current research topic is the precise alignment of the sample and the reconstructed master wavefront so that the resulting phase map only contains information of the differences in shape or deformation. The reconstructed master wavefront can be adjusted digitally to correctly illuminate the sample object, by introducing an artificial phase-shift. This phase-shift is induced by the LCD, and offers also the possibility of calibrating precisely the set-up. The value for the phase-shift is obtained by a comparison of the resulting interferogram with a database containing fringes from simulations of misalignments between master and sample objects. Using the iterative algorithm described here, the correction of the sample position can be controlled by an automatic adaptation of the coherent mask.

Paper Details

Date Published: 15 September 2006
PDF: 6 pages
Proc. SPIE 6341, Speckle06: Speckles, From Grains to Flowers, 63410Y (15 September 2006); doi: 10.1117/12.695339
Show Author Affiliations
Xavier Schwab, Univ. Stuttgart (Germany)
Eugen Meister, Univ. Stuttgart (Germany)
Giancarlo Pedrini, Univ. Stuttgart (Germany)
Wolfgang Osten, Univ. Stuttgart (Germany)

Published in SPIE Proceedings Vol. 6341:
Speckle06: Speckles, From Grains to Flowers
Pierre Slangen; Christine Cerruti, Editor(s)

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